Thursday, 6 August 2015

Cryptic diversity: A new species of Wolf from Africa.

Cryptic species are species which
closely resemble other species and which can only be separated by careful
anatomical examination or even genetic analysis. In recent years the widespread
application of DNA analysis to populations of wild animalshas led to the discovery that many
well-known species are in fact clusters of cryptic species, with profound
implications for the conservation of these species; a single large widespread population
suddenly becoming a number of smaller more localized populations.

Golden Jackals, Canis aureus, from North Africa have
long been noted for being larger and more robust than Jackals from either
Sub-Saharan Africa or Eurasia, leading to speculation that they may represent a
separate species or sub-species. A study published in 2011 in the journal PLoS One based upon analysis of mitochondrial DNA found that Jackals from Egypt and Ethiopia were
in fact not Jackals at all, but were more closely related to the Grey Wolf, Canis lupus, and suggested that these should
be described as a separate subspecies of Wolf, the African Wolf, Canis lupus lupaster. A follow-up study
published in the same journal in 2012 found that the mitochondrial lineage
ascribed to Canis lupus lupaster was
also present in Canids in West Africa, among animals considered to be more
typically Jackal-like.

All of the African Jackals were
found to be a separate species from the Eurasian Jackals, and more closely
related to the Eurasian Grey Wolf. However these African Wolves appear to have
separated from their Eurasian cousins over a million years ago, and were judges
sufficiently genetically distinct to be placed in a separate species.
Examination of taxonomic records for Canids revealed that the French biologist
Cuvier had described a ‘Jackal’ from Senegal as a separate species, Canis anthus, in 1820, an analysis that
was rejected by subsequent biologists who failed to spot any significant
morphological difference between African and Eurasian Jackals. For this reason
Koepfli & Pollinger et al.
suggest that African Golden Jackals henceforth be referred to as African Golden
Wolves, Canis anthus, rejecting Canis lupus lupaster as a valid name.

Phylogenetic Tree Based on Mitochondrial Cytochrome b Sequences and
Sampling Localities of Golden Jackals Used in This Study (A) Maximum-likelihood
phylogram of 104 cytochrome b sequences (1,140 bp). Haplotype number is shown
next to taxon name and locality. Accession numbers indicate sequences
downloaded from GenBank. Haplotypes without accession numbers are novel
sequences generated for the present study. Asterisks at nodes indicate
bootstrap support R80% based on maximum-likelihood analyses (500 pseudoreplicates)
and R0.95 posterior probability from Bayesian inference. Canis spp. from Egypt are indicated by thick arrows. Haplotypes
labeled as Canis lupus lupaster refer
to the African wolf. The tree was rooted using Sechuran Fox (Lycalopex sechurae) as outgroup. Scale
bar indicates the number of substitutions per site. Photo credits: left, Golden
Jackal from Senegal (CIBIO/Monia Nakamura); centre, Mexican Gray Wolf (Tom and Pat Leeson); right, Golden Jackal from Israel (Eyal Cohen). (B) Map of
geographic localities showing where Golden Jackals were sampled. Relative
number of animals sampled from each locality is shown. Hatched lines indicates
geographic range of Golden Jackal based on International Union for the Conservation of Nature distribution. Koepfli & Pollinger et al. (2015).

Morphologically the African
Golden Wolf and Eurasian Golden Jackal are very hard to tell apart, other than
the distinct largeness of the North African specimens; the African Wolf was, on
average slightly broader in the snout than the Eurasian Jackal, but not
distinctively enough for this to be used as a reliable feature to distinguish
the species.

The Golden Jackal samples from
Israel were found to be mostly hybrid animals, containing DNA from Eurasian
Golden Jackals, Grey Wolves, African Golden Wolves and Dogs. Two Golden Wolves
from Egypt were found to have mitochondrial DNA (which is passed through the
female line without recombination) from Eurasian Jackals and Grey Wolves,
suggesting that hybridization was occurring here too, though whole genome
analysis of Egyptian samples was not carried out.

Comparison of the genomes of
African Golden Wolves and Dogs suggest that a small amount of Dog DNA derives from
African, rather than Grey Wolves; this is roughly comparable to the amount of
Neanderthal DNA found in modern Humans, with two groups of Dogs, the Basanji
(African Laughing Dog) and Dingo, having higher levels of Golden Wolf DNA than
other groups.

This scenario suggests that
Africa has repeatedly been invaded by different Canid lineages from Eurasia.
Koepfli & Pollinger et al.
suggest that this relates to the changeable climate of the Pleistocene Era,
with warmer wetter periods when it was possible for Canids to move between
Eurasia and Africa, and cooler dryer periods when these populations became
reproductively isolated.

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About Me

Studied Palaeobiology & Evolution at the University of Portsmouth, Geosciences via the Open University & Ecology and Conservation at Christchurch University, Canterbury.
Have worked in wildlife based tourism, mineral exploration, development, conservation, education & environmental chemistry. Occasionally write articles for papers and magazines.

This Blog would be impossible without the work of countless scientists (and others) throughout the world. Where possible I do my best to credit them, but there will always be many more who remain unmentioned; this does not imply I am ungrateful for their contributions. Any errors or inaccuracies are, of course, my own.